Turbidity reaction PRACTICAL Flashcards
Describe the reaction which investigates how chnages in concentration affects the rate of reaction
- Use a measuring cylinder to pur 10cm^3 of sodium thiosulfate solution into a connical flask
- Place the connical flask on a printed ‘X’ mat
- Pour 10cm^3 hydrochloric acid into the connical flask
- Swril the connical flask, start a stopwatch
- Look down itno the connical flask, you will see the solution start to turn cloudy
- Stop the stopwatch when you can no longer see the ‘X’
- Repeat the experiment using lower concentrations of sodium thiosulfate solution.
- Repeat each experiment 3 times to calculate the mean time value for each of the concentrations
What might a problem be with this rate of reactions practical?
It may not be reproducible
What does reproducible mean?
A measurement is reproducible if it is done by a different person or done with different equipment/technique and you still get the same results
Why might this experiment not be reproducible?
Different students have different eyesights,they may be able to see the ‘X’ longer than others - it disappears at different times- so they may not get the same results
Why migt the problem witht the practical not being reproducible not be the biggest problem
The cross on the mat is printed the same size for all students, so it may not be the biggest problem
how would you measure the rate of the reaction in this experiment?
Turbidity practical
quantity of product/time
if a prodcut is formed (solution goes cloudy) use 1/time
if not use 0/time
units are number/second (as we never measured the mass)
What is the name of the white precipitate that turns the solution cloudy?
Solid Sulfur
A student draws a different cross for each experiment with a different concentration.
What problem would this cause?
[1 mark]
the crosses may be
darker or may not be the same size/shape
What an experiment called when different students do the same experiment and get similar results
Reproducible
